Main Article Content
Hypofractionated radiotherapy (HFRT) in breast cancer treatment regimen (40 Grey /15 fractions/3 weeks) is more convenient for patients, especially those coming from remote areas to radiotherapy facilities and for healthcare providers, than conventional fractionation (50 Gy/25 fractions/5weeks). So the effect
of radiotherapy interruption on treatment outcome (loco-regional control (LRC)& overall survival (OS)) during hypofractionated schedule is the issue of our study.
Materials and Methods: We studied retrospectively 174 female patients with breast cancer who received PORT at the Clinical Oncology & Nuclear Medicine Department, Faculty of Medicine, Mansoura University, Egypt, from January-2012 to December-2016. We determined the treatment outcome (OS&LRC) from the follow-up (FU) of the studied patients, as the patient still survived or died, and recurrence till now occurred or not, and were estimated with the Kaplan-Meier (K-M) method and Logrank test, respectively. Then we calculated surviving fraction (SF) and tumor control probability (TCP) with regard to biologically effective dose (BED), for all patients, using breast cancer radiobiological parameters.
Results: When comparing patients without radiotherapy gap with patients with radiotherapy gaps, the results showed a decrease in LRC rate in patients with radiotherapy treatment interruptions by 15 % (P=0.019, a significant value), but no detrimental effect on OS because of the very limited number of the studied patients. Curves of the relationship between (SF&OTT) and (TCP&OTT) confirmed the detrimental effect of unscheduled gap during radiotherapy fractions on the treatment outcome. Also we found a significant-P value for (marital status, start day of radiotherapy fractions, time, number, and duration of gaps); it means these factors affect LRC during radiotherapy interruptions.
Conclusions: Interruptions during postoperative hypofractionated irradiation of breast cancer (40 Gy/15 fractions/3weeks) should be avoided and if they are inevitable, they should not be prolonged more than two days, as they will adversely affect the treatment outcome (LRC).
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors retain the copyright of their manuscripts, and all Open Access articles are distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided that the original work is properly cited.
The use of general descriptive names, trade names, trademarks, and so forth in this publication, even if not specifically identified, does not imply that these names are not protected by the relevant laws and regulations. The submitting author is responsible for securing any permissions needed for the reuse of copyrighted materials included in the manuscript.
While the advice and information in this journal are believed to be true and accurate on the date of its going to press, neither the authors, the editors, nor the publisher can accept any legal responsibility for any errors or omissions that may be made. The publisher makes no warranty, express or implied, with respect to the material contained herein.
 Carlson R. W., Allred D. C., Anderson B. O., Burstein H. J., Edge S. B., Farrar W. B., Forero A., Giordano S. H., Goldstein L. J., Gradishar W. J., Hayes D. F., Hudis C. A., Isakoff S. J., Ljung B. M. E., Mankoff D. A., Marcom P. K., Mayer I. A., McCormick B., Pierce L. J., Reed E. C., Smith M. L., Soliman H., Somlo G., Theriault R. L., Ward J. H., Wolff A. C., Zellars R., Kumar R., and Shead D. A., (2012), “Metastatic breast cancer, version 1.2012: featured updates to the NCCN guidelines.” Journal of National Comprehensive Cancer Network; 10: [821-829].
 Chen Hui Tan, Ting-Ting Chao, Jui-Chen Liu, Chun-Hung Lin, Yung-Sung Huang, Chung-Ming Chang, Hon- Yi Lin, Yu-Chieh Su, Yen-Lin Chen, and Ching-Chih Lee, (2016), “Breast cancer therapy and age difference in cardiovascular disease risks: A population-based cohort study in Taiwan.” Taiwanese Journal of Obstetrics & Gynecology; 55: [98-103].
 Fisher B., Anderson S., Bryant J., Margolese R. G., Deutsch M., Fisher E. R., Jeong J.-H., and Wolmark N., (2002), “Twenty-year follow-up of a randomized trial comparing total mastectomy, lumpectomy, and lumpectomy plus irradiation for the treatment of invasive breast cancer.” The New England journal of medicine; 347: [1233–1241].
 Veronesi U., Cascinelli N., Mariani L., Greco M., Saccozzi R., Luini A., Aguilar M., and Marubini E., (2002), “Twenty-year follow-up of a randomized study comparing breast- conserving surgery with radical mastectomy for early breast cancer.” The New England Journal of Medicine; 347: [1227– 1232].
 Overgaard M., Hansen P. S., Overgaard J., Rose C., Andersson M., Bach F., Kjaer M., Gadeberg C. C., Mouridsen H. T., Jensen M. B., and Zedeler K., (1997), “Postoperative radiotherapy in high-risk premenopausal women with breast cancer who receive adjuvant chemotherapy.” Danish Breast Cancer Cooperative Group 82b Trial. The New England Journal of Medicine; 337: [949– 955].
 Overgaard M., Jensen M. B., Overgaard J., Hansen P. S., Rose C., Andersson M., Kamby C., Kjaer M., Gadeberg C. C., Rasmussen B. B., Blichert-Toft M., and Mouridsen H. T., (1999), “Postoperative radiotherapy in high-risk postmenopausal breast-cancer patients given adjuvant tamoxifen: Danish Breast Cancer Cooperative Group DBCG 82c Trial.” Lancet; 353: [1641–1648].
 Poortmans P., (2007), “Evidence based radiation oncology: breast cancer.” Radiotherapy and Oncology; 84: [84–101].
 Mondal D. and Sharma D. N., (2016), “External beam radiation techniques for breast cancer in the new millennium: New challenging perspectives.” Journal of the Egyptian National Cancer Institute; 28: [211–218].
 Elsayed M. Ali and Magdy Khalil Abd AlMageed, (2014), “Post-mastectomy Hypofractionation Radiotherapy in Breast Cancer Patients.” Cancer and Oncology Research; 2: [87-93].
 Bese N. S., Sut P. A., and Ober A., (2005), “The effect of treatment interruptions in the postoperative irradiation of breast cancer.” Oncology; 69: [214-223].
 Royal College of Radiologists (RCR), (2008), “The timely delivery of radical radiotherapy: standards and guidelines for the management of unscheduled treatment interruptions. 3rdedition.” London: The Board of Faculty of Clinical Oncology.
 Bese N. S., Sut P. A., Sut N., and Ober A., (2007), “The impact of treatment interruptions on locoregional control during postoperative breast irradiation.” Journal of BUON; 12: [353-359].
 Fowler J. F., (2010), “21 years of Biologically Effective Dose.” The British Journal of Radiology; 83: [554-568].
 Hedman M., Björk-Eriksson T., Brodin O., and Toma-Dasu I., (2013), “Predictive value of modelled tumour control probability based on individual measurements of in vitro radiosensitivity and potential doubling time.” The British Journal of Radiology; 86: .
 Douglas W. Arthur, Frank A. Vicini, David E. Wazer, and Atif J. Khan, (2016), “Short Course Breast Radiotherapy. A Comprehensive Review of Hypofractionation, Partial Breast, and Intra-Operative Irradiation.”Springer International Publishing Switzerland.
 Fowler J. F., (1989), “A Review: The linear quadratic formula and progress in fractionated radiotherapy.” The British Journal of Radiology; 62: [679-694].
 Paul Jacobs, Aaron Nelson, and Ian Liu, (2012), “Biological Effective Dose and Tumor Control Probability Modeling using the MIM® Software Suite.” WHITE PAPER, MIM Software Inc., 25200 Chagrin Blvd. Cleveland, Ohio 44122• 866-421-2536 • www.mim software.com
 Hennequin C. and Dubray B., (2013), “Le rapport alpha/ bêta revisité à l’heure de l’hypofractionnement.” Cancer/ Radiothérapie; 17: [344-348].
 Cancer Group Institute, (2011), “Currently Recruiting Breast Cancer Clinical Trials.” www.cancergroup.com
 Xinfeng Liu, Sara Johnson, Shou Liu, Deepak Kanojia, Wei Yue, Udai P. Singh, Qian Wang, Qi Wang, Qing Nie, and Hexin Chen, (2013), “Nonlinear Growth Kinetics of Breast Cancer Stem Cells: Implications for Cancer Stem Cell Targeted Therapy.” SCIENTIFIC REPORTS; 3: . DOI: 10.1038/srep02473,
http: // www. nature. Com/scientificreports.
 Kaplan E. L. and Meier P., (1958), “Nonparametric estimation from incomplete observations.” J Am Stat Soc B; 53: [457–481].
 Nitin Ohri, Bruce D. Rapkin, Chandan Guha, Shalom Kalnicki, and Madhur Garg, (2016), “Radiation Therapy Noncompliance and Clinical Outcomes in an Urban Academic Cancer Center.” International Journalm of Radiation Oncology*Biology*Physics; 95: [563–570].